Process control systems incorporate emergency shutdown valves which are normally in a fully opened or fully closed state. In order to assure that such emergency shutdown valves can properly function, they are periodically tested by partially opening or closing these valves. Since these tests are typically performed with pressure in the pipeline of the process control system, it is important to perform any test quickly and then return the valve to its normal state.
In such prior emergency shutdown systems, in order to perform a short test, a complicated panel of pneumatic valves and switches are normally used by an operator to partially open or close the emergency shutdown valve under test. In particular, this requires an operator to observe and understand a panel of pneumatic valves and switches and then to operate the particular associated valves and switches in order to partially open or close the desired emergency shutdown valve being tested. It is also important that any emergency shutdown system provide the ability to be able to move the emergency shutdown valve to its safe condition when commanded by the emergency shutdown controller, in the unlikely, but possible situation where a failure event has occurred during a valve test interval, and the valve under test must now be properly commanded by the emergency shutdown system.